Strategies for Assessing the Implications of Malformed Frogs for Environmental Health

Burkhart, James G.; Ankley, Gerald T.; Bell, Heidi; Carpenter, Hillary M.; Fort, Douglas J.; Gardiner, David M.; Gardner, Henry; Hale, Robert C.; Helgen, Judy C.; Jepson, P. C.; Johnson, Douglas H.; Lannoo, Michael J.; Lee, David; Lary, Joseph M.; Levey, Rick B.; Magner, Joe; Meteyer, Carol U.; Shelby, Michael D.; Lucier, George W.

doi:10.2307/3454299

Cited by 18 publications

(18 citation statements)

References 22 publications

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“…The types of deformities I observed encompass those seen in other studies reporting increases in abnormalities from around North America (12)(13)(14)(16)(17)(18)(19)(20)(21). The strong context dependence observed in this study may help explain the disparities among the observations of deformities under natural conditions and those experimentally induced under laboratory conditions that have been reported in numerous studies (13).…”

Section: Discussionsupporting

confidence: 58%

“…Given evidence for the role of metacercariae in limb deformities, it will be important to determine whether metacercariae can be shed after they induce limb deformities. Such a pattern could explain the occurrence of deformities in wild collected frogs that are not associated with metacercariae (12)(13)(14).…”

Section: Discussionmentioning

confidence: 99%

“…In addition, for some populations, unprecedented mortality has been documented (7)(8)(9)(10)(11). Included within these reports are accounts of increases in developmental deformities (12)(13)(14). Amphibian deformities, in particular those related to limb development, have now been reported in 43 states in the U.S. and in five Canadian Provinces, as well as in several other countries around the world (13).…”

mentioning

confidence: 93%

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Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?

Kiesecker

2002

Proc. Natl. Acad. Sci. U.S.A.

377

348

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The apparently rapid increase in the prevalence of amphibian limb deformities has led to substantial interest from ecologists and public health professionals. Hypotheses proposed to explain the deformities fall into two broad categories: chemical contaminants and trematode infection. Although there are convincing experimental demonstrations that certain factors can lead to some deformities, the causes for recent increases in amphibian malformation remain controversial. Moreover, no experimental studies on amphibian deformities have been conducted in the field, and no studies have attempted to examine the synergistic effects of trematode infection and exposure to chemical contaminants. Here, I present the results of field and laboratory experiments that link increased trematode infection, and increased limb deformities, to pesticide exposure. Field experiments conclusively demonstrated that exposure to trematode infection was required for the development of limb deformities in wood frogs, Rana sylvatica. However, deformities were more common at sites adjacent to agricultural runoff. Laboratory experiments corroborated the association between pesticide exposure and increased infection with pesticide-mediated immunocompetency as the apparent mechanism. Given the conservative contaminant exposure levels used [Environmental Protection Agency (EPA) drinking water standards] and the widespread use of many pesticides, these negative impacts may help to explain pathogen-mediated amphibian declines in many regions.

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Section: Discussionsupporting

confidence: 58%

Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 93%

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Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?

Kiesecker

2002

Proc. Natl. Acad. Sci. U.S.A.

377

348

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“…Amphibian embryos can be more susceptible to chemical stress than fishes [38] and moreover some studies point out that even water quality features in unpolluted places could be also related to adverse effects on amphibian embryos [39][40]. Taking into account that 2,4-D and copper could be employed in the same environmental scenarios, the information on their synergistic effect on no target species as in this case Bufo arenarum embryos, could be valuable for the protection of endangered species and for more customized environmental risk assessment.…”

Section: Resultsmentioning

confidence: 99%

Synergistic Effects of Copper and Butylic Ester of 2,4-Dichlorophenoxyacetic Acid (Esternon Ultra) on Amphibian Embryos

Pérez-Coll

Herkovits

2006

IJERPH

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Abstract:Cu 2+ and butylic ester of 2,4-Dichlorophenoxyacetic acid as Esternon Ultra (2,4-D) toxicity on Bufo arenarum embryos were evaluated by means of a short-term chronic toxicity test (AMPHITOX). The NOEC values for Cu and 2,4-D were 0.02 mg/L and 2 mg/L respectively. The toxicity profile curves for Cu and 2,4-D were reported. The interactions of the metal and the herbicide were evaluated by combined treatments with different concentrations of Cu and 2,4-D. Although in all cases, a synergistic effect between these chemicals was observed, the combination of concentrations exerting low level effects in isolated treatments resulted in more adverse embryonic survival. Considering that both products are extensively used in agroecosystems, this fact could be of concern for non target species like amphibians.

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“…Although the explanation for the degradation of amphibian populations is currently disputed, Pechmann et al (8) caution that it may be difficult to distinguish natural population fluctuations from human-induced declines without long-term surveys at numerous sites to isolate the various confounding components. However, anthropogenic factors such as water pollution and atmospheric conditions such as ozone depletion and/or UV radiation could play important roles (4,6). Continuing population reductions and morphologic defects in anurans has generated international interest.…”

mentioning

confidence: 99%

Mitogen-activated protein kinase activation by oxidative and bacterial stress in an amphibian cell culture model.

Carter

Tabor

Bonner

et al. 2002

Environ Health Perspect

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The decline of many amphibian species could be caused by their susceptibility to environmental pollutants that cause cellular stress and cell death. A variety of intracellular signal transduction pathways are activated by environmental stress factors, which result in cell death. Mitogen-activated protein kinases are intracellular signaling molecules that include the extracellular signal-regulated kinases (ERK-1 and ERK-2). We used cultured (italic)Xenopus(/italic) tadpole cells (XTC-2 cells) to investigate the activation of ERK by oxidative or bacterial stress, two environmental factors that could contribute to pollution in aquatic systems. We exposed XTC-2 cell monolayers to hydrogen peroxide or bacterial lipopolysaccharide and measured ERK activation by Western blotting using antibodies raised against phosphorylated ERK-1 and ERK-2. Only ERK-2 was detected in XTC-2 cells. Both hydrogen peroxide and lipopolysaccharide caused ERK-2 phosphorylation in a time- and concentration-dependent manner. Hydrogen peroxide caused a 20- to 30-fold increase in ERK-2 activation that peaked 30 min after treatment, and lipopolysaccharide induced a 5- to 10-fold increase in ERK-2 activation that peaked 60 min after treatment. PD98059, an inhibitor of the ERK pathway, reduced the cytotoxic response of XTC-2 cells to hydrogen peroxide or lipopolysaccharide. These data suggest that ERK-2 is an intracellular target of oxidative and bacterial stress in amphibians that mediates, at least in part, the cytotoxic response to hydrogen peroxide or lipopolysaccharide. Moreover, the (italic)Xenopus(/italic) (XTC-2) cell culture system could serve as a useful model to identify agents that might threaten amphibian populations and human health.

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Strategies for Assessing the Implications of Malformed Frogs for Environmental Health

Cited by 18 publications

References 22 publications

Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?

Synergism between trematode infection and pesticide exposure: A link to amphibian limb deformities in nature?

Synergistic Effects of Copper and Butylic Ester of 2,4-Dichlorophenoxyacetic Acid (Esternon Ultra) on Amphibian Embryos

Mitogen-activated protein kinase activation by oxidative and bacterial stress in an amphibian cell culture model.

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